Wu Cheng 吳澄 (1249-1333), courtesy name Wu Youqing 吳幼清 or Wu Boqing 吳伯清, style Caolu xiansheng 草廬先生, was a Confucian scholar of the Yuan period 元 (1279-1368)
. He came from Chongren 崇仁 in the prefecture of Fuzhou 撫州, Jiangxi, and was a disciple of Cheng Ruoyong 程若庸, who directly belonged to the circle around Zhu Xi 朱熹 and his school, represented by Rao Lu 饒魯. When the Mongols conquered the Southern Song empire 南宋 (1127-1279) and united China in the Yuan empire, he was recommended by Cheng Jufu 程鉅夫 and four times traveled to the capital Dadu 大都 (modern Beijing). At the occasion of his fourth visit he was made Director of Studies in the Directorate of Education (guozi siye 國子司業), then junior compiler in the Historiography Institute (guoshiyuan bianxiu 國史院編修), auxiliary academician (zhixueshi 直學士) in the Academy of Scholary Worthies (Jixianyuan 集賢院), and finally lecturer of the Classics colloquium (jingyan jiangguan 經筵講官), but then decided to retire and become a private teacher, like Zhu Xi had been. While Wu Cheng was the most famous Confucian teacher in southern China, Xu Heng 許衡 had a great name in northern China.
His own philosophy did not clearly discern between Zhu Xi's "philosophy of the Heavenly principle" (lixue 理學) and Lu Jiuyuan's 陸九淵 "philosophy of the mind" (xinxue 心學), and his aim was to reconcile the two traditions. Wu Cheng explained that between Heaven and Earth, the two "substantial energies" (qi 氣) Yin and Yang were active, as well as the Five Virtues (wude 五德) and the Five Desires (wuyu 五欲), but all were controlled by the Heavenly principle (li 理). This principle was inherent in and inseparable from substance (qi 氣). It was the duty of the Confucian practitioner to preserve his mind (cun xin 存心) and to enlighten the principle (ming li 明理). The wise man would have a spirited mind and apply his wisdom (xin ling 心靈, zhi yong 智用) in a moral way. Wu observed that that the concept of the "originary mind" (benxin 本心) was in fact not invented by Lu Jiuyuan, but had also been a fundamental idea of the sage rulers of the past, Yao 堯 and Shun 舜, Confucius and his diciples, Mengzi 孟子, and also the early Neo-Confucian masters like Zhou Dunyi 周敦頤, the brothers Cheng Hao 程顥 and Cheng Yi 程頤, Zhang Zai 張載 and Shao Yong 邵雍. The teachings of the two schools (of Lu Jiuyuan and Zhu Xi), he said, were therefore in fact only one.
Wu Cheng's most important studies of the Confucian Classics were Wujing zuanyan 五經纂言 and Sanli kaozhu 三禮考注; he also wrote a commentary to the book Laozi 老子, Daodejing zhu 道德經注, and the biji "brush notes" style book Caolu jingyu 草廬精語. His collected writings are called Caolu Wu Wenzhenggong wenji 草廬吳文正公文集.